Partial combustion or gasification of coal involves reaction of the coal at elevated temperatures, and possibly elevated pressures, with a limited volume of oxygen, the reaction preferably being carried out in a reactor or reaction chamber or vessel by means of "burners" in the presence of additional agents such as steam, carbon dioxide, or various other materials. Gasification of coal produces a gas, known as synthesis gas, that contains mostly carbon monoxide and hydrogen. Also produced are varying minor quantities of other gases, such as carbon dioxide and methane, and, at least with some coals, various heavier materials, such as small sticky or molten particles. In some processes, the design of the gasifier or reactor is such that the sticky or molten particles are carried downward principally by the synthesis gas through a water quench area or zone, and thence to a slag recovery area. Remaining fine particles, now solidified, pass with the synthesis gas from the bottom of the quench zone or cyclones, where the particles are separated.
In at least one other coal gasification process undergoing development, the design of the gasifier is such that a rough separation of the molten particles takes place in the gasifier vessel or chamber. That is, the heavy particles drop to the bottom of the gasifier vessel to a slag recovery area or bath, and lighter and molten particles are carried by the synthesis gas upward and out of the reactor chamber into a quench zone which is mounted generally above the gasifier, and wherein a cool quench gas is employed to quench the gas and particles. The particles carried upward, in the aggregate, tend to be of somewhat different chemical composition than the "slag" which falls to the bottom of the vessel, and are designated collectively herein as "flyslag." The solidified material, because it is derived from a "reducing" atmosphere, may be different in composition and properties from flyash normally associated with combustion boilers, wherein a fully oxidizing atmosphere is utilized. For example, the flyslag from processes for partial combustion of coal may contain elemental iron and sulphides, components not normally associated with boiler flyash.
A significant concern in processes where the molten or sticky particles are transported up into the quench zone is the possibility that the flyslag particles will stick to the walls of the quench zone. Unlike the down-fired processes, where water may be present or injected to quench and help wash down the particles, a quench gas, such as a cool recycle gas, may be employed, along with indirect heat exchange, for quenching and cooling the synthesis gas and the sticky or molten particles. Sticking of the flyslag particles will cause loss of heat transfer, and, of greatest concern, possibly result in plugging of the quench zone. The invention addresses this problem.